This project is based upon the utilization of a non-invasive canopy-spirometer-computer system for the prolonged measurement of spirometry and gas exchange in normal adult subjects and in patients with various surgical diseases. The spirometry signals are obtained without touching the face, or the upper airway, of the individual and computer processing on-line yields a series of graphs, which provide a detailed summary of the study for prompt review. An ongoing study is being conducted to define the breathing pattern as a function of age and sex when the artifacts of conventional measuring equipment are not present. This data is to serve for comparison with measurements of acutely ill surgical patients, with special attention to tidal volume, frequency, minute ventilation, inspiratory and expiratory time, mean inspiratory flow rate and mean expiratory dwell time. Preliminary studies have established the feasibility of this system for measuring the response to ventilatory stimulation using inspired CO2, or measured amounts of supine exercise. Such studies are being adapted for use with surgical patients, where the simultaneous response in gas exchange and ventilatory pattern may characterize the patient's physiologic and metabolic reserve in a new way. Our long range goal is to provide earlier recognition of the loss of breathing reserve and a more sensitive means of following the results of ventilatory therapy. Current studies are being carried out to examine the influence of intravenous nutrients on the breathing pattern and ventilatory drive of depleted and acutely injured patients.